The utility model discloses an elasticity is from hasp, including the base and detain the body, to detain the body inboard and be equipped with movable groove, the activity groove outside is equipped with spacing portion, and detain the body lower extreme and be equipped with two card holes perpendicularly, detaining and still being equipped with not closed annular on one's body and detaining the arm, the right -hand member is good at to the arm was detained to the annular left end, the annular detain two extreme points on the arm respectively with detain two mutual zonulae occludens in card hole on one's body, arm activity in activity inslot is detained to the annular. The utility model discloses simple structure, can make under the condition that does not set up the spring buckle the arm can be through the metal elasticity playback auto -lock of self, its low cost can apply to extensively that case and bag are detained, fields such as the (window) curtain is buckled, lobster knot, key ring.